Principal Commercial Commitments under Repurchase Agreements and Dealer Inventory Financing Guarantees (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011
Guarantee On Dealer Inventory Financing
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Total Amount Committed	$ 900	$ 1,684
Term of Commitments	Various
Standby Repurchase Obligations On Dealer Inventory Financing
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Total Amount Committed	$ 861,738	$ 791,933
Term of Commitments	Up to eighteen months